fix tox env

Author: Gagaro

tox.ini

@@ -10,7 +10,7 @@ envlist =
     {py35,py36,py37}-djangomaster
 
 [testenv]
-commands = coverage run ./quicktest.py leaflet --db=$DATABASE
+commands = coverage run ./quicktest.py leaflet --db={env:DATABASE:}
 deps =
     django18: Django>=1.8,<1.9
     django19: Django>=1.9,<1.10
@@ -22,6 +22,7 @@ deps =
     djangomaster: https://github.com/django/django/archive/master.tar.gz
     argparse
     coverage
+passenv = DATABASE
 
 [travis:env]
 DJANGO =